JPH0569770B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is a smectite that swells in water and has excellent gel-forming, ion-exchange, and film-forming abilities, and also has special functions such as inclusion of metal polynuclear hydroxide ions and various organic substances between layers. The present invention relates to a novel swellable silicate having a structure and a method for producing the same. Smectite is a member of phyllosilicates that has a three-layer structure of the Sanderutsch type, consisting of two silica tetrahedral layers sandwiched between a magnesium octahedral layer or an aluminum octahedral layer, and has cation exchange ability in water. It is a clay mineral that exhibits the unique property of swelling by absorbing water between its layers. Naturally known smectites such as montmorillonite and beidellite, which are 2-octahedral smectites containing trivalent aluminum in the octahedral layer, and hectorite and saponite, which are 3-octahedral smectites containing divalent magnesium in the octahedral layer, are known. It is being Utilizing the swelling properties, gel properties, and inclusion properties of these smectites, attempts are being made to develop applications in fields such as water-based paints, cosmetics, pharmaceuticals, and catalysts, and natural products and synthetic products are being targeted. ing. Regarding natural products, bentonite containing montmorillonite is the only product produced on an industrial scale in Japan, and pure montmorillonite, which is extracted from this bentonite, is commercialized, but it is expensive due to extremely high refining costs. There are also problems with its characteristics, and demand is limited. Also, chemical composition,
Due to large fluctuations in material properties such as structure, defects, and impurities, properties cannot be controlled, making it unsuitable as a highly functional precision material. On the other hand, sodium-type tetrasilicon mica (JP-A-51-24598) products, which are synthetic swelling fluorinated mica-based minerals, are commercially available as gelling agents, but the mica structure originally makes it difficult to swell in water. Therefore, its swelling properties in water tend to be somewhat poor, and since its assemblability is almost constant, it is almost impossible to control the chemical composition, so its demand as a functional precision material is limited. . The purpose of the present invention is to develop a novel swellable silicate, which has higher functionality than commercially available sodium-type tetrasilicon mica products and whose chemical composition can be controlled, as a designable precision material that is industrially satisfactory. Our goal is to provide manufacturing technology. The present inventors have conducted intensive research for many years on the synthesis of swellable silicates having excellent cation exchange ability or gel-forming ability. Published Patent Publication Showa
The present invention led to the invention of a new swellable silicate having a structure similar to that of 59-21517) and special functions such as excellent gel-forming ability, ion-exchange ability, and film-forming ability, and a method for producing the same. That is, this invention has the general formula [(SiO ₂ ) ₈ (MO _2/3 ) _a (MgO _2/3 ) _b (OH) _2/3(a+b)
+cd F _d ] ^c-・A ^y+ _c/y () (The values of a, b, c, d and y in the formula are 0<a
≦6,0≦b<6,3<a+b≦6,0<c≦
2,0≦d≦2/3(a+b)+c and 1≦y≦
2, and M is Co, Ni, Zn, Cd, Cu, Fe, Mn,
At least one divalent heavy metal ion selected from Pb, etc., and A is at least one cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions, and alkylammonium ions. ) and a method for producing the same. McEwan (Montmorillonite minerals by
DMC MacEwan, The X-ray identification
and crystal structures of xlay minerals
edited by G.Brown, Mineralogical society,
London, 1972, pp. 143-207), the layer charge of hectorite, which belongs to the 3-octahedral smectite, is caused by the substitution of part of the divalent magnesium in the octahedral layer with monovalent lithium. It is believed that in saponite, which also belongs to the tri-octahedral smectite, a part of the tetravalent silicon in the tetrahedral layer is replaced with trivalent aluminum, so that negative charges are generated. On the other hand, the present inventors had previously succeeded in synthesizing a new smectite from only silicon, magnesium, and cations (Publication of Patent Publication No. 1986-
21517), it has been clarified that when silicon 8 is used, it can be manufactured in a wide composition range with an amount of magnesium in the range of 3 to 10. In this structure of magnesium smectite, the charge balance between magnesium in the octahedral layer and the oxygen, hydroxyl group or fluorine coordinated to it shifts to the negative charge side due to the presence of a slight excess of hydroxyl group or fluorine. It is said that this occurs due to These 3-octahedral smectites have cations between the layers to electrically balance the layer negative charges. The novel swellable silicate of the present invention represented by the general formula ( , copper, iron, manganese,
It has a structure substituted with divalent heavy metal ions such as lead. The above-mentioned magnesium smectite itself does not exist naturally, and therefore, the swellable silicate of the present invention containing a large amount of the above-mentioned divalent heavy metal is considered to be a completely new smectite. A method for achieving the present invention will be described below. The method for producing a synthetic swellable silicate of the present invention consists of the following steps. First, a homogeneous composite precipitate containing silicon, divalent heavy metals, and optionally magnesium is prepared, and second, water and optionally exchangeable cations or fluorine ions are added to the homogeneous composite precipitate. to obtain a starting material silary, thirdly to subject the slurry to a hydrothermal reaction to produce a swellable silicate, and fourthly to obtain the product of the present invention by drying and pulverizing this hydrothermal reaction product. I can do it. In the first step, a homogeneous solution obtained by mixing silicic acid, a divalent heavy metal salt and, if necessary, a magnesium salt is precipitated with an alkaline solution, and by-product solutes are removed by filtration and water washing to form a homogeneous composite precipitate. be adjusted. A homogeneous solution containing silicic acid and a divalent heavy metal salt and, if necessary, a magnesium salt can be prepared by mixing the silicic acid solution and a divalent heavy metal salt aqueous solution and adding an aqueous magnesium salt solution if necessary, or by directly adding divalent heavy metal salt to the silicic acid solution. Obtained by dissolving a heavy metal salt and, if necessary, a magnesium salt. The mixing ratio of silicic acid, divalent heavy metal salt, and magnesium salt is determined by selecting the values of a and b within a range that satisfies the general formula (). (a+
The value of b) is between 3 and 6, although normally preferred values are between 5 and 6. Although it is preferable that the charging composition satisfies the general formula (), the swellable silicate of the present invention can be produced even if the value of (a+b) is varied slightly more than 6, and values up to about 6.5 are acceptable. be done. The synthetic swellable silicate of the present invention can be synthesized even with a composition containing no magnesium, where b=0. A silicic acid solution is obtained by mixing sodium silicate and mineral acid and making the pH of the solution acidic.
As the sodium silicate, any of commercially available No. 1 to No. 4 water glass and sodium metasilicate can be used. Nitric acid, hydrochloric acid, sulfuric acid, etc. are used as mineral acids. When mixing sodium silicate and mineral acid, gelation often occurs if the amount of mineral acid is small, so it is necessary to select the ratio of sodium silicate and mineral acid so that the pH of the liquid is 5 or less. Divalent heavy metal salts can be selected from chlorides, sulfates, nitrates, etc. of cobalt, nickel, zinc, cadmium, iron, manganese, lead, and the like. If the amount satisfies the composition of general formula (), there are not only one type of heavy metal but also two types of heavy metals.
It is possible to select from any combination of compositions over types, and compositions can be designed according to the application.
It is also possible to add a magnesium salt if necessary, and it can be selected from magnesium chloride, magnesium sulfate, magnesium nitrate, etc. Next, a homogeneous solution containing silicic acid and a divalent heavy metal salt or, if necessary, a magnesium salt, and an alkaline solution are mixed at room temperature to obtain a homogeneous composite precipitate. As the alkaline solution, sodium hydroxide solution, potassium hydroxide solution, aqueous ammonia, etc. are used.
It is desirable to select the amount of alkaline solution such that the pH after mixing is 10 or higher. When the homogeneous solution and the alkaline solution are mixed, the homogeneous solution may be dropped into the alkaline solution to cause precipitation, or the reverse order may be used. A homogeneous composite precipitate can also be obtained by instantaneously mixing both liquids. Next, filtration and washing with water are repeated to sufficiently remove by-product solutes. According to X-ray powder diffraction, these homogeneous composite precipitates containing heavy metals already have a low-crystalline smectite-like structure, and therefore, in the third step, hydrothermal treatment at a relatively low temperature and for a short time is required. It is inferred that the synthetic swellable silicate of the present invention having better properties is produced by this method. Furthermore, since the above-mentioned homogeneous composite precipitate often already incorporates cations at the time of precipitation, there is no particular need to add exchangeable cations in the second step. The starting material slurry for the second step is prepared by adding water and, if necessary, a cationic hydroxide, fluoride, or a mixed aqueous solution thereof to the homogeneous composite precipitate obtained in the first step, or adding hydrofluoric acid to the homogeneous composite precipitate obtained in the first step. Adjusted by adding It is not particularly necessary to add cations, but if they are added, it is desirable to add them in an amount given by c/y. y is given the valence number of the cation to be added, and is 1 or 2 in the case of one type of cation. c is a value between 0 and 2,
Usually the preferred value is between 0.5 and 1.2, and usually a value around 0.8 should be chosen. The amount of cations to be added is permissible up to about four times the value of c. The swellable silicate of the present invention can be synthesized without adding fluoride ions, but when added, the value of d may be selected within the range of 0 to 2/3 (s+b)+c. If the value of (a+b) is 6,
Assuming that c=0.8, the amount of fluorine ions can be selected between 0 and 4.8 in terms of calculation, but addition up to about twice the amount of 4.8 is permissible. In the hydrothermal reaction of the third step, the raw material slurry obtained in the second step is charged into an autoclave and subjected to a hydrothermal reaction at a temperature of 100° C. to 350° C. to produce the swellable silicate of the present invention. Although stirring is not particularly required during the reaction, stirring is absolutely prohibited. In general, the higher the reaction temperature, the faster the reaction rate, and the longer the reaction time, the better the crystal formation, but at a reaction temperature of 200°C and a reaction pressure of 15.9 kg to cm ^{2 ,} a reaction time of 2 to 3 hours is sufficient. In the fourth step, after the completion of the hydrothermal reaction in the third step, the contents of the autoclave are taken out and heated to a temperature above 60℃.
The final product is obtained by drying at a temperature below 200°C and grinding. The novel synthetic swellable silicate produced by carrying out the present invention was determined by X-ray diffraction, differential thermal analysis, infrared absorption spectrum, chemical analysis, cation exchange capacity (CEC), viscosity properties, etc. can be evaluated based on The novel swellable silicate of the present invention has a diffraction angle (2θ) of (hk) reflection when using Cu-Kα radiation (35,
06), it appears between 59.5 degrees and 61 degrees, indicating that it is a 3-octahedral smectite. The X-ray diffraction pattern is similar to that of hectorite and saponite, but the peaks are generally broad in many cases. Usually 50-120 in aqueous solution
Exhibits high cation exchange capacity of milliequivalents to 100g,
Alternatively, it shows excellent swelling properties and dispersibility in water, produces a colored aqueous gel corresponding to the type of heavy metal, and has thixotropic properties.
Additives for water-soluble paints, cosmetics, ceramic raw materials, catalysts, slurry stabilizers, colorants, thickeners,
It is extremely useful as a binder, suspension stabilizer, thixotropy agent, etc. Since the novel swellable silicates of the present invention essentially contain divalent heavy metals,
It can also be used for purposes such as sterilization, antibacterial, insect repellent, and disinfection. In addition, it is possible to incorporate heavy metals with strong catalytic activity into the structure in various proportions, making it useful as a catalyst and catalyst carrier.Furthermore, it can form interlayer complexes with various metal polynuclear hydroxide ions, making it a novel material. It can be used as a catalyst, catalyst carrier, adsorbent, etc. Furthermore, by forming an organic compound composite, it can be used as a lipophilic clay as a gelling agent for various organic solvents, a thixotropy imparting agent, etc., or as a filler for polymeric materials, a composite material, etc. It can also be fired and used as ceramics, and is useful as sensors, electromagnetic shielding materials, radiation shielding materials, semiconductors, etc. Next, an example will be given and explained. Example 1 Put 400ml of water into the beaker 1, and add No. 3 water glass (SiO ₂ 28%, Na ₂ O 9%, molar ratio 3.22)
Dissolve 86 g and add 23 ml of 16N nitric acid at once while stirring to obtain a silicic acid solution. Next, dissolve 71.3 g of cobalt chloride hexahydrate special reagent (purity 99%) in 100 ml of water, add it to the silicic acid solution to prepare a homogeneous mixed solution, and add it to 400 ml of 2N sodium hydroxide solution while stirring. Drip in minutes. The reaction homogeneous composite precipitate immediately obtained was filtered, thoroughly washed with water, and then washed with water.
Add 20ml to make a slurry and transfer to an autoclave. React at 15.9Kg/cm ² and 200°C for 3 hours.
After cooling, the reaction product is taken out, dried at 80°C, and then crushed using a grinder. This product contains cobalt as M, a=6, b
=0, c=0.57, d=0, it contained sodium as an exchangeable cation, and its cation exchange capacity was 60 milliequivalents to 100 g. The X-ray powder diffraction pattern shows a pattern similar to hectorite and saponite, which are 3-octahedral smectites, but the peaks are broad overall, and the d value of the (35,06) reflection peak is 1.544 Å. Ta. The powder was purple in color and the 2% aqueous dispersion formed a purple translucent thixotropic solid gel. Example 2 The same procedure as in Example 1 was carried out except that the amounts of raw materials charged were as follows. No. 3 water glass 86g Nickel chloride () hexahydrate special grade reagent (purity 98
%) 71g 10% hydrofluoric acid 10ml The product obtained has a green color and contains nickel as M, corresponding to a = 6, b = 0, c = 0.61, d = 1, and as an exchangeable cation. It contained sodium and had a cation exchange capacity of 64 meq/100g. The X-ray powder diffraction pattern was similar to the pattern of the inventive product of Example 1, and the d value of the (35,06) reflection peak was 1.525 Å. The 2% aqueous dispersion formed a thixotropic green translucent solid gel. A 2.5% aqueous dispersion was prepared using the products of the present invention obtained in Examples 1 and 2 and a commercially available synthetic sodium-type tetrasilicon mica product as an aqueous dispersant, and its rheological properties were determined by rotational viscosity. The table shows the results measured with a Fann VG meter.

[Table] As is clear from the table, the aqueous dispersion of the cobalt-containing inventive product of Example 1 and the nickel-containing inventive product of Example 2 was compared with the aqueous dispersion of a commercially available synthetic sodium-type tetrasilicon mica product. It can be seen that it has high viscosity, yield value, and gel strength at low rotational speeds, and has excellent performance as a gelling agent for aqueous systems.

Claims (1)

[Claims] 1 General formula [(SiO ₂ ) ₈ (MO _2/3 ) _a (MgO _2/3 ) _b (OH) _2/3(a+b)
+cd F _d ] ^c-・A ^y+ _c/y (The values of a, b, c, d and y in the formula are 0<a
≦6,0≦b<6,3<a+b≦6,0<c≦
2,0≦d≦2/3(a+b)+c and 1≦y≦
2, and M is Co, Ni, Zn, Cd, Cu, Fe, Mn,
At least one divalent heavy metal ion selected from Pb, etc., and A is at least one cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions, and alkylammonium ions. ) is a swellable silicate with a structure similar to smectite. 2. In synthesizing the swellable silicate having a structure similar to smectite as set forth in claim 1, a combination of silicic acid, divalent heavy metal salt, and magnesium salt satisfying the composition of the general formula set forth in claim 1 is used. After preparing a homogeneous composite precipitate from a homogeneous mixed solution and an alkaline solution and removing by-product solutes, the slurry prepared by adding water and, if necessary, cations or fluorine ions, is heated at 100°C to 350°C. 1. A method for producing a swellable silicate, which comprises carrying out a hydrothermal reaction, followed by drying and pulverizing the reaction product.